JP2658080B2 - Wheel slip prevention control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Summary of the Invention >> The present invention controls an actuator for increasing or decreasing the pressure of brake hydraulic oil in accordance with a wheel slip amount obtained from a vehicle speed and a wheel rotation speed obtained by integrating a vehicle acceleration. The purpose of the present invention is to provide a wheel slip prevention control device that eliminates a calculation error of a wheel slip amount caused by integration of vehicle body acceleration and enables reliable control. The vehicle speed is estimated by offsetting and integrating by a fixed amount, and when the vehicle speed is exceeded by the wheel rotation speed, the vehicle speed is set as an initial value of the integration. It is characterized in that a wheel slip amount is obtained based on a high wheel rotation speed.

<< Industrial Application Field >> The present invention provides an actuator for increasing or decreasing the pressure of a brake hydraulic fluid based on a slip amount of a wheel based on a vehicle speed and a wheel rotation speed obtained by integrating a vehicle acceleration. The present invention relates to a wheel slip prevention control device to be controlled.

<< Prior Art >> With respect to this type of apparatus, Japanese Patent Publication No. 51-6305 is known, and FIG. 2 shows an example of a conventional apparatus.

In the figure, a vehicle body acceleration a is detected by an acceleration detector 10 and a rotation speed Vw of a wheel is detected by a wheel speed detector 12.
Has been detected.

The wheel rotation speed Vw is time-differentiated by a differentiation circuit 14, and the wheel acceleration obtained by the differentiation circuit 14 is compared with a comparison circuit.
Given to 16,18.

The set accelerations of 0.6G and -1.0G are given to the comparison circuits 16 and 18, respectively.
Are provided to the AND circuit 24 through the respective circuits.

Further, the comparison signal of the comparison circuit 18 is given to the integration circuit 26, and the integration circuit 26 performs the time integration of the vehicle body acceleration a by the acceleration detector 10 which initially sets the wheel rotation speed Vw when the comparison signal is input. Has been started.

The estimated vehicle speed Vi obtained by this integration is the wheel rotation speed
It is provided to the slip ratio calculation circuit 28 together with Vw, and the slip ratio S of the wheel is calculated based on the values.

The comparison circuit 30 compares the wheel slip ratio S by the slip ratio calculation circuit 28 with the set slip ratio 0.15, and the comparison signal is given to the AND circuit 24 via the inversion circuit 32.

Further, in the comparison circuit 34, the wheel rotation speed Vw and the set vehicle speed 5 km /
is compared with the comparison signal h, and the comparison signal is supplied to the AND circuit 38 together with the comparison signal of the comparison circuit 16 and the comparison signal of the comparison circuit 30 inverted by the inversion circuit 36.

The AND signal of the AND circuit 38 is a flip-flop 40
And the S input of the flip-flop 40 is supplied with the comparison signal of the comparison circuit 34.

The Q signal of the flip-flop 40 is given to the OR circuit 42, and the OR circuit 42 is given a clock pulse from the pulse generator 44.

Further, the OR signal of the OR circuit 42 is given to the AND circuit 24, and the AND signal of the AND circuit 24 is output to the actuator for increasing / decreasing the pressure of the brake oil via the terminal 46 as a pressure increase or intermittent pressure increase control signal. Have been.

The AND signal of the AND circuit 38 is supplied to a terminal 48, and is output to the actuator as a pressure reduction control signal of the brake hydraulic oil via the terminal 48.

This example is configured as described above. When the vehicle starts running, the flip-flop 40 is set by the comparison circuit 34.

When the wheel rotation acceleration by the differentiating circuit 14 becomes -1.0 G, the time integration of the vehicle body acceleration a with the wheel rotation speed Vw at that time as an initial value is started by the integration circuit 26, and the slip ratio calculation circuit 28 The estimated vehicle speed Vi approximately equal to the vehicle speed is given from that time.

During the subsequent running of the vehicle, when the wheel rotation speed by the differentiating circuit 14 is between -1.0 G and 0.6 G, the slip ratio S is 0.
When the pressure increase condition of 15 or less is satisfied, a pressure increase control signal is output from the terminal 46 to the actuator.

As a result, the pressure of the brake oil is rapidly increased linearly as indicated by a characteristic 300 in FIG. 3 (E), and the wheels are immediately braked.

When the pressure increasing condition is not satisfied, the AND circuit 24
Output of the pressure increase control signal is stopped, and the pressure of the brake working oil is maintained as it is.

If the wheel rotation speed is 0.6G or less and the slip ratio S is 0.15 or more, the pressure reduction condition is satisfied, and the pressure reduction control signal by the AND circuit 38 is output from the terminal 48 to the actuator, whereby the pressure of the brake hydraulic oil is reduced. Wheel slip is avoided.

Further, when the pressure reduction condition is not satisfied, the output of the pressure reduction control signal is stopped, and the pressure of the brake hydraulic oil is maintained.

When the pressure-increasing condition is satisfied again, the flip-flop 40 is reset when the pressure-decreasing condition is satisfied. Therefore, the pressure-increasing control signal is sent from the AND circuit 24 to the actuator via the terminal 46 at the clock pulse cycle of the pulse generator 44. Output, whereby the pressure of the brake hydraulic oil rises stepwise at a low speed and the braking force of the wheels is gradually increased.

After that, pressure maintenance, pressure reduction, maintenance,
The pressure increase is repeated.

<< Problems to be Solved by the Invention >> However, in the related art, since the slip amount of the wheel is obtained by using the vehicle speed obtained by integrating the vehicle acceleration as it is, the error of the slip ratio is detected by the detection error of the vehicle acceleration. Accumulates, making it difficult to accurately control the slip amount.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a wheel slip prevention control device that can always perform accurate control by eliminating the above-described accumulated error.

<< Means for Solving the Problems >> In order to achieve the above object, the device of the present invention is configured as follows.

First, the acceleration of the vehicle body is detected by the vehicle body acceleration detecting means, and the acceleration is offset by a certain fixed amount by the acceleration offsetting means.

Then, the offset acceleration is integrated by the vehicle body speed estimating means, whereby the vehicle speed is estimated.

Further, the rotational speed of the wheel is detected by the wheel rotational speed detecting means, and a higher one of the vehicle speed based on the rotational speed and the estimated vehicle speed is selected by the vehicle speed selecting means.

When the vehicle speed based on the wheel rotation speed is selected from these, the speed is set by the integration initial value setting means at a constant cycle as the integration initial value.

The slip amount of the wheel is calculated by the slip amount calculating means based on the selected vehicle speed and the detected wheel rotational speed. The actuator for increasing or decreasing the pressure of the brake fluid is controlled by the brake hydraulic pressure control means in accordance with the slip amount. Is controlled by

<< Operation >> In the present invention, during non-braking, the estimated speed of the vehicle body by integrating the vehicle body acceleration is always lower than the vehicle body speed by the wheel rotation speed, and is reset to the vehicle body speed by the wheel rotation speed at a constant cycle.

When the vehicle speed based on the wheel rotation speed falls below the estimated vehicle speed by braking, the slip amount of the wheel is obtained using the vehicle speed.

Therefore, at the time of this braking, an accurate vehicle body speed is estimated by integrating the actual vehicle speed immediately before that as an initial value, and the actuator is controlled using the accurate slip amount.

<< Description of Examples >> Hereinafter, preferred examples of the device according to the present invention will be described with reference to the drawings.

In FIG. 1, the vehicle acceleration a obtained by the acceleration detector 10 is given to an adding circuit 50, and the adding circuit 50 is given a constant acceleration -0.1G.

Accordingly, the vehicle acceleration a is offset by 0.1 G in the addition circuit 50, and the acceleration a thus offset is given to the integration circuit 26.

In the integration circuit 26, the offset acceleration a is time-integrated with the wheel rotation speed Vw of the wheel speed detector 12 provided via the switch circuit 52 as an initial value, and the integration value I
Corresponds to the estimated vehicle speed.

The integrated value I of the integration circuit 26 is given to a comparison circuit 54, and the comparison circuit 54 is given the wheel rotation speed Vw by the wheel speed detector 12.

The comparator 54 compares the magnitudes of the two inputs. When the integrated value I is larger, the switch circuit 56 is turned on. When the wheel rotation speed Vw is larger, the switch circuit 58 is inverted. It is driven ON via the circuit 60.

These switch circuits 56 and 58 have an integrated value I of the integrating circuit 26.
And the wheel rotation speed Vw of the wheel speed detector 12 are given.
To the estimated vehicle speed Vi.

Therefore, the higher one of the vehicle speed based on the integration of the offset vehicle acceleration a and the vehicle speed based on the wheel rotation speed Vw is selected and used by the slip ratio calculation circuit 28 to calculate the slip ratio S.

The inverted signal of the inverting circuit 60 is given to the AND circuit 64, and the AND circuit 64 is given the clock signal of the pulse generator 66.

Therefore, in the AND circuit 64, the wheel rotation speed Vw is determined by the integration circuit.
When the integrated value I is larger than 26, an AND signal of a pulse train synchronized with the pulse generator 66 is obtained, and the AND signal is supplied to the switch circuit 52 via the OR circuit 68.

The switch circuit 52 is driven ON by this AND signal. As a result, the wheel rotation speed Vw is given to the integrating circuit 26 via the switch circuit 52 as an initial value of the offset acceleration a at a cycle determined by the AND signal of the AND circuit 64. Can be

Further, the OR signal of the OR circuit 68 is given to the reset input of the integrating circuit 26. Therefore, when the vehicle speed by the wheel rotation speed Vw exceeds the vehicle speed by integration of the offset acceleration a, the integrated value I The wheel rotation speed Vw is reset with the cycle as an initial value.

The comparison signal of the comparison circuit 54 is given to the monostable multivibrator 70.

In the monostable multivibrator 70, an output pulse is obtained when the wheel rotation speed Vw is inverted from a state where the wheel rotation speed Vw is smaller than the integral value I to the opposite state, and this output pulse is output to the integration circuit 26 via the OR circuit 68. The reset input and the switch circuit 52 are provided.

As a result, when the wheel rotation speed Vw exceeds the integration value I, the integration value I is initially reset to the wheel rotation speed Vw.

FIG. 3 illustrates the operation of this embodiment. In FIG. 3A, the integral value I, the wheel rotation speed Vw, and the estimated vehicle speed Vi are shown.
And the actual vehicle speed V are shown.

2B shows the output pulse of the monostable multivibrator 70, FIG. 2C shows the clock pulse of the pulse generator 66, FIG. 2D shows the comparison signal of the comparison circuit 54, and FIG. FIG. 5E shows the state of the pressure change of the brake hydraulic oil.

Here, until time t ₀ no braking operation is performed, the vehicle is traveling at a constant speed.

Therefore, the integrated value I of the integrating circuit 26 decreases with a time constant determined by the offset amount 0.1G, and is initially reset to the wheel rotation speed Vw at the clock pulse generation interval of the pulse generator 66.

Therefore, during this constant speed traveling, although the integral value I is always lower than the wheel rotational speed Vω, it is initially reset at a fixed interval, so that it is almost always equal to the actual vehicle speed V.

Brake operation in a subsequent time t ₀ is started, when the integrated value I below the wheel speed Vw, the integrated value I is estimated vehicle speed Vi
The slip ratio S is obtained by the slip ratio calculation circuit 28 based on the estimated vehicle speed Vi and the wheel rotation speed Vw.

When the pressure increasing condition described above is satisfied from the slip ratio S and the wheel rotational acceleration by the differentiating circuit 14, the pressure of the brake hydraulic oil is sharply increased according to the characteristic 300 as shown in FIG. Is not satisfied, the hydraulic pressure at that time is maintained as it is.

When the above-described pressure reducing condition is satisfied, the hydraulic pressure of the brake hydraulic oil is controlled to decrease, and when the condition is not satisfied, the hydraulic pressure at that time is maintained as it is.

When the pressure increase condition is satisfied again, the flip-flop
Since 40 is reset in advance when the pressure reduction condition is satisfied,
As shown in FIG. 3 (E), the hydraulic pressure of the brake operating oil slowly rises in a stepwise manner, and the wheel braking force is gradually increased.

At this time, if the wheel rotation speed Vw exceeds the integral value I, the third
As shown in FIG. (A), the integral value I is added to the wheel rotation speed Vw at that time.
Is initially reset.

As described above, according to the present embodiment, the estimated vehicle speed based on the integral of the vehicle acceleration almost coincides with the actual vehicle speed until immediately before braking, and the estimated vehicle speed based on the integral using this as an initial value at the time of braking. Since the slip amount of the wheel is obtained from the wheel speed and the wheel rotational speed, the slip amount is extremely high in accuracy, and therefore, it is possible to always perform highly accurate control.

<< Effects >> As described above, according to the present invention, since the vehicle speed is estimated by integrating the vehicle acceleration with the actual vehicle speed immediately before braking as an initial value during braking, the wheel slip amount can be accurately obtained. Thus, highly accurate control is possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional example, and FIG. 3 is a graph illustrating the operation of the embodiment. 10 Acceleration detector 12 Wheel speed detector 24 AND circuit 26 Integration circuit 28 Slip ratio calculation circuit 30 Comparison circuit 38 AND circuit 40 Flip-flop 42 OR circuit 44 pulse generator 50 adder 52 switch circuit 54 comparison circuit 56, 58 switch circuit 60 inversion circuit 62 addition circuit 64 AND circuit 66 pulse generator 68 …… OR circuit 70 …… Monostable multivibrator

Claims (1)

(57) [Claims] 1. A vehicle acceleration detecting means for detecting an acceleration of a vehicle body, an acceleration offset means for offsetting the detected acceleration by a fixed amount, and a vehicle speed for estimating a vehicle speed by integrating the offset acceleration. Estimating means; wheel rotational speed detecting means for detecting the rotational speed of the wheels; vehicle body speed selecting means for selecting a higher one of the estimated vehicle speed and the vehicle speed based on the detected wheel rotational speed; When a vehicle speed is selected based on the speed, integration initial value setting means for setting the speed as an initial value of the integration at a constant cycle; and a wheel based on the selected vehicle speed and the detected wheel rotation speed. And a brake fluid pressure control means for controlling an actuator for increasing or decreasing the pressure of the brake fluid in accordance with the slip amount. A wheel slip prevention control device, comprising: